The goal is to design, build, and test an ultrafast laser scanner microscope capable of acquiring high-resolution image data at a data rate of 64 MHz for use in automated prescreening for cancer. A prototype of an ultrafast, automatic laser scanning microscope is under construction. The instrument will be capable of acquiring image data sampled at 0.5 micron intervals and will be tested for automated prescreening of cancer. All subsystems (i.e., laser source, polygon scanner, autofocus, sensor system, and digital electronics) have been tested in a breadboard configuration. Cell images have been recorded using either of two wavelengths, 570 and 630 nanometers. Output signals are currently fed through an A/D converter into a Grinell display and back through a D/A converter to provide a visual image on a monitor. Chief modification of the breadboard to prototype is the switching of the optical train to a vertical configuration, which allows the slide to be scanned in a horizontal plane. The prototype unit will operate at 48 MHz, the speed being limited by the maximum rotational speed of the polygon at 36,000 RPM. (3)